In recent years, disk devices, such as magnetic disk drives, optical disc drives, etc., have become widely used as external recording devices of computers and image recording devices.
In general, a disk device, for example, a magnetic disk drive (HDD), comprises a housing and a printed circuit board (PCB) opposed to the bottom surface of the housing. The housing accommodates a recording medium, magnetic head, actuator configured to move the magnetic head, etc. An insulator (insulating sheet or film) is interposed between the PCB and the bottom surface of the housing.
In recent HDDs, the recording surface density of a magnetic disk is so high that it is more and more difficult to improve the actuator control accuracy. There is a method of achieving a required equipment performance in this situation. According to this method, the actuator control accuracy is improved by providing, on the PCB of the HDD, a rotational vibration sensor (or acceleration sensor, hereinafter referred to as the “RV sensor”) for detecting vibration in the direction of rotation relative to the actuator.
Although the vibration detection by the RV sensor is highly effective for suppressing simple vibration in the rotational direction of the actuator, the vibration may sometimes produce noise, thereby reducing the improvement effect of the actuator control accuracy, in the case where the PCB itself vibrates.
Accordingly, a proposal has been made to use a foam material with damping properties for the insulator interposed between the PCB and the housing of the HDD. However, the use of this type insulator as a component results in an increase in material cost. Although a flat insulating sheet and film are low-cost insulators, they cannot meet the requirement of damping performance.